This invention relates in general to audiovisual systems for recording and conveying information between people. More specifically, it relates to an improved automatic pointer apparatus that superimposes a highlighting spot on a sequence of visual images, moves the highlighting spot over each image under manual control in continuous coordination with the recording of an audio program, and records movement-controlling signals for subsequently automatically moving the highlighting spot on playback with the audio program.
A variety of audio and audiovisual systems record information presented by a speaker or operator and play it back to an audience of one or more people. One such audiovisual system is described in U.S. Pat. No. 4,146,314 that is assigned to the assignee of this invention. That patent discloses several forms of automatic pointer apparatus for moving a highlighting spot over visual images in close coordination with an accompanying recorded audio program. In this apparatus, a control device continuously and rapidly generates a series of electrical signal sets. Each signal set corresponds to a two-dimensional position that is selected manually by an operator. Specifically, the control device is hand-held. The operator's movement of a control actuator on the control device, that may include a joy stick, a stylus, or even a finger, produces variations in the amplitudes of analog signals that form the signal sets.
Periodically the signal sets are sampled and converted into digital form and then converted into a frequency-shift-keyed form that is suitable for recording on a first, or control, track of a multiple track magnetic tape, along with control information that is also produced in freuqency shift keyed form. The recording of this information on the control track occurs simultaneously with the recording of the operator's spoken words or some other audio program on a second, or audio, track.
The frequency-shift-keyed signals are also reconverted simultaneously into digital form for driving stepping motors to position a pointer mechanism that projects the highlighting spot on the visual image. Thus, the highlighting spot follows the movement of the control actuator only after the signal sets from the control actuator are sampled, converted into frequency-shift-keyed form, and reconverted into digital form. During playback of the magnetic tape, the recorded signals in frequency-shift-keyed form from the control track on the tape are converted into digital form for driving the stepping motors so that the highlighting spot follows the signals recorded on the control track of the magnetic tape and thus retraces the path of the spot during the recording operation.
When a program is recorded with this apparatus, an operator must coordinate two distinct actions. The first is the spoken part of the program in which he records a prepared discussion of the visual images that are projected. The second is a projector control function that includes changing slides and, with the apparatus shown in the aforementioned patent, utilizing the control actuator to move the highlighting spot in conjunction with the oral presentation. As will be apparent, it is very desirable that this control function be quickly learned and become essentially automatic, or second nature. If it is not, the operator must, to a certain extent, concentrate on the control function. This detracts from his concentration on the audio function and can introduce interruptions, pauses, and repetitions in the audio program that detract from the overall effect of the program when it is played back.
It has been found that the apparatus disclosed in U.S. Pat. No. 4,146,314 could distract an operator during the recording of a program. One cause of the distractions seems to be the series of conversions of the signal sets from the control actuator to digital signals, to frequency-shift-keyed signals, and then back to digital signals for controlling the stepping motors. The conversions are based upon discrete samples of the analog signal sets from the control actuator, and each of the serial conversions requires a discrete time interval. Thus, there is a noticeable interval between the time the operator moves the control actuator to a new position and the arrival of the highlighting spot at a new position on a screen. Secondly, stepping motors were used to simplify the structure of the drive while still providing a low mass, inexpensive, reliable mechanism. However, stepping motors by definition "step" from one position to another, and this "stepping" operation also contributes a sense of discrete, jerky motions, especially when the stepping motors operate in response to the discontinuous signals that result from continuous movement of the control actuator.